IL41893A - Printing inks for sublimation transfer printing - Google Patents

Description

f rintiiig inks for sublimation ransfer printing CIB&-GBIGT i G, Qi -40102 The present invention provides novel printing inks with organic solvents for sublimation transfer printing. These inks are particularly stable and contain a high concentration of sublimable dyes in very fine dispersion.

Organic printing inks are already known from German Offenlegungsschrift 1 771 813 which contain (1) a dye which sublimes at 160° to 220°C or a dyestuff mixture, (2) a soluble resin which acts as dyestuff carrier, (3) an aqueous organic or practically pure organic solvent or solvent mixture, and (4) a resin which acts as thickener or binder for the printing ink. The resins in (2) and (4) can be identical. Practically all organic solvents which possess a satisfactory solubility or emulsifiability for the dyes and binders to be used are described as useful. Mixtures, for example of an aliphatic ketone and an aromatic hydrocarbon, are also cited as suitable. In addition, the use of alcohols, such as butanol and benzyl alcohol, is also said to be advantageous.

It is known further from British patent 1 295 634 to manufacture printing inks based on oils customarily used in the printing ink industry, e.g. mineral oils, drying ^or semi-drying oils, by themselves or together with synthetic resins such as modified phenol resins. As a rule such preparations; have a high viscosity, especially whenever a substantial amount of dye, i.e. more than. %, is to be incorporated. Moreover, the dye is in partly dissolved, partly dispersed form, so that the colours are not uniform and are unstable.

In addition, these compositions have various disadvantages which complicate their industrial use.

For example, they can lead to a "moirage" effect (unlevel-ness of the printing design displaying an unsettled, cloudy appearance). This feature results in rejects owing to staining and, in addition, in a reduction of the printing speed. This would appear to be a separation phenomenon, a creaming, which comes about through individual dyes preferring to dissolve in one part of the solvent and thus causing the formation of a second liquid phase.

A further significant disadvantage is the gradual formation of coarse crystals which lead to doctor streaks and scratches on the rollers. They are evidently formed by amounts of solvent oversaturated with dissolved dye reprecipitating the dye by crystallisation on storage.

The invention is based on the observation that it is possible to manufacture stable printing inks which display no recrystallisation and which no longer display this moirage effect, by using specific organic solvents or mixtures thereof with specific synthetic resins or mixtures of such resins.

Surprisingly, it has transpired that those solvents or solvent mixtures which are able to dissolve the dye at room temperature to a maximum extent of 2 g/1, preferably l'g/1, yield particularly stable inks which do not show evidence of all the cited disadvantages.

The invention therefore provides printing inks for sublimation transfer printing which contain a disperse dye or a dyestuff mixture in fine dispersion, sublimable at 160°-220°C and free from water-soluble dispersing agents, and one or more synthetic resins used as dyestnff carriers, stabilisers, thickeners, and binders, isaid printing inks containing weight a) a fluid, low moleculai, organic solvent or solvent mixture, in which the individual dyes are soluble to a maximum of 0.2% at room temperature and the synthetic resin or resins are soluble to at least 5%, and b) have a viscosity of at most 30 seconds, measured in a Ford measuring cup 4, with a content of at least 15% of dye and at least 5% of synthetic resin.. Suitable solvents which fulfil the cited requirements are the low molecular aliphatic hydrocarbons with a boiling point between 80°C and 180°C, the first members of the aliphatic alcohols and, in particular, mixtures of both these solvent types.

If possible, they should be free from aromatic hydrocarbons and ketones. The mixtures in particular are very good solvents for the required synthetic resins, but very poor ones for the disperse dyes, and yield extremely stable printing inks of low viscosity. The solubility of the dyes in the printing ink should not be greater than 2 g/1 and preferably should be below 1 g/1. Mention may be made of the following hydrocarbons: 2,2- and 2,3-dimethyl butane, isohexane, 3-methyl- and 2,4-dimethyl pentane, n-heptane, n-octane5 ii-decane, n-undecane, cyclohexane, meth lcyclopentane and, in particular, mixtures with boiling limits between 110° and 180°C. Methanol, ethanol, propanol, isopropanol, isobutanol, and tertiary butanol may be cited as alcohols. Particularly suitable are mixtures of isopropanol with methanol, ethanol or n-propanol, or with a liquid aliphatic hydrocarbon or hydrocarbon mixtures whose boiling point is between 80° and 180°C, preferably between 110° and 140° C.

Suitable hydrocarbons or hydrocarbon mixtures which are liquid at room temperature and whose boiling points are betwee 80° and 180° C are straight-chain or branched products as well as those which have a cycloalkyl group. As examples of such solvents which can be used in admixture with isopropanol there may be cited: 2,2-and 2, 3-dimethylbutane, isohexane, 3-methyl- and 2,4- d i-meth l-pentane, n-heptane, n-octane, n~decane, n-un-decane, cyclohexane, methylcyclopentane, methylcyclohexane , l-isopropyl-4-methylcyclohexane and, in particular, n-hexane and mixtures, such as petroleum distillates with boiling ranges between 110°C and 180°C.

The term "dyestuffs" also comprises water-insoluble optical brighteners which display the sublimab ility i-equired according to the invention. Suitable disperse dyes, i.e. dyes which are free from diluents and are preferably almost insoluble in water, are those which in an interval of 15 to 25 seconds, but at most 100 seconds, sublime at 160° to 220°C to at least 60% from the support to a fabric and fix fast in the substrate. By this is meant that they are not just superficially deposited and can be washed out, for example in cold acetone.

The following dyes, for example, can be mentioned: the dyes of the general formula wherein X is a sulphonic acid ester, carboxylic acid ester, carboxylic acid amide or, preferably, a cyano radical, the radicals and are optionally substituted alkyl radicals and A is an optionally substituted para-phenylene radical, or the dyes of the formulas: The dyes are practically insoluble in the solvents and solvent mixtures according to the present invention, i.e. at room temperature they have a solubility which is preferably in the region of 0.17o, whereas the dyestuff concentration of the ink is as a rule about one hundred times greater. They are therefore in the form of a fine dispersion with a particle size which should preferably be below 10 . The synthetic resins or their mixtures, which must be present in the printing ink in solution, have a number of functions to fulfil. They must stabilise the dyestuff dispersions so that no sedimentation or creaming occurs; they must guarantee the reversibility of the dispersion in the event of small amounts of the printing ink drying out and falling back into the printing ink; they must give the colour sufficient body and ensure a good film quality without increasing the viscosity above the limit still permissible for printing. They must rapidly release the solvent and may not be tacky. They may not retain the dye during the transfer and must withstand the requisite temperatures without undergoing change or decomposition. In order to meet all these requirements and at the same time to incorporate large amounts of dyestuff into the printing ink, it is practically unavoidable to work with a combination of various synthetic resins whose properties are complementary or cumulative. The cellulose alk lethers and -esters have here a particularly important function to fulfil as stabilisers of the dyestuff dispersion.

Besides phenyl cellulose, alkylcellutbse, cyano- ethyl cellulose, and ethylhydroxyethyl cellulose, especially ethyl or propyl cellulose may be considered suitable. Among the esters particular mention may be made of the alcohol- soluble mixed ester, for example cellulose acetobutyrate or cellulose acetopropionate. Particular interest attaches to the readily soluble products of low viscosity with not too high molecular weight.

It is advantageous to kept the content of ethyl cellulose as low as possible in order not to increase the viscosity too greatly. Preferably another synthetic resin is used to give the .printing ink the required amount of be "body". This resin must also dissolve readily and/free from sediment in the combination rapidly release the solvent, and not become tacky on drying. Synthetic resins which fulfil these conditions and possess the necessary heat stability for the transfer method are to be found in the classes of colophonium derivatives, in particular the esters of hydrogenated or polymerised colophonium •which is optionally modified with phenols and resin formers such as acrylic acid. To be cited further are the alkyd resins, the maleinate resins, the polyterpenes , the polyvinyl acetals, the alkylated polyolefines , the substituted rubbers such as chlorinated and cyclised rubber, and the ketone resins. By means of preliminary tests it is easy to establish whether the viscosity and solubility satisfy the requirements, also whether the solvent mixture is released rapidly enough. the Compared with the printing inks of/prior art, the , transfer printing inks according to the present invention possess moreover the great advantage that it is possible to .manufacture concentrated preparations of high dye-stuff content, e.g. 10-40% of pure dyestuff, as is necessary for application in flexographic printing- and for trans fer prdnting on carpets. They therefore constitute a valuable advantage in the art.

The printing inks can be manufac ured by methods which are known per se, for example by dilution, while stirring, of finel)' dispersed dyestuff preparations which contain the sublimable dyestuffs mentioned hereinbefore and synthetic resins.

The most advantageous procedure is to prepare in advance the disperse dyestuffs which are free from water-soluble dispersants and diluents firstly with one or more of the necessary synthetic resins, for example by substrate grinding in solvents or water, optionally with subsequent spray drying. It is also possible to manufacture these preparations by salt mastication in trough kneaders with the addition of solvents with swelling action.

Processes and preparations of this kind are described in French patent 1 535 547. By far the most universal process, and that which is less severe on the synthetic resins, is the two-phase coating process for obtaining dyestuff preparations according to Belgian patent 759 779. These preparations contain, the dyestuff in the right degree of division and only require to be stirred into the solvent mixture to which is added subsequently the amount of synthetic resin required to adjust the viscosity.

The carriers necessary for the transfer printing can be any kind of -preferably non-textile - structures, preferably flat shaped structures on a cellulose basis, which are printed with the printing inks according to the invention. Very deep prints are obtained, so that it is possible to use the same auxiliary carrier optionally more than once for the transfer printing. Paper is chiefly used as carrier.

The following Examples illustrate the invention, the parts and percentages being by weight unless otherwise stated.

Example 1 While stirring 16 parts of a preparation consisting of 12 parts of the finely dispersed dye of the formula H and 4 parts of ethyl cellulose are made into a paste with 60 parts of methanol and 60 parts of isopropanol. A stable printing ink is obtained. A paper is printed therewith and dried. The paper is heated together with a web of polyacrylonitrile fibres for 30 seconds at 180° C in a press. A fast, full print is obtained.

A similarly good result is achieved by using ethanol, n-propanol or n-hexane instead of methanol.

Example 2 16 Parts of a preparation consisting of 12 parts of the finely dispersed dye of the formula and 4 parts of ethyl cellulose are processed to a printing ink as described in Example 1. A red preparation is obtained which has similarly good properties.

A similarly good violet printing ink is obtained by using the dye of the formula instead of that used herein before.

Example 3 A mixture of finely dispersed dyestuffs of the following formulae and containing 50% ethyl cellulose are mixed in the ratio 12 parts of yellow 0 KH with 18 parts of methanol and 70 parts of isopro anol and filtered through gauze. A strong printing ink free of residue is obtained.

Ex m le 4 While stirring for 10 minutes, 7.5 parts of a preparation consisting of 3.75 parts of the finely dispersed dye of the formula and 3.75 parts of ethyl cellulose are dispersed in a mixture consisting of 22 parts of isopropanol, 22 parts of ethanol (S67o) , and 44 parts of petroleum spirit (boiling ranges 110-140°C) which contain 4.5 'parts of ethyl cellulose in solution to raise the viscosity. The resulting printing ink has a viscosity of 24 sees. (Ford 4) and is very sta le. After the printing ink has been stored for several months the dye displays no solution or re-crystallisation phenomena which impair roller printing on paper.

Example 5 A series of finely dispersed dyes tuf s which contain 50% ethyl cellulose and have the following constitutions are mixed to a brown in the ratio and dispersed in 45 parts of isopropanol and 45 parts of Isopar E (a petroleum spirit with a boiling range of 116-141°C which is practically free from aromatic substances and marketed by the Esso Petroleum Company) with the addition of 4.33 parts of ethyl cellulose. The printing ink is very stable and after storage for several months displays no loss in quality when it is stirred briefly.

Example 6 parts of a preparation consisting of 3.75 parts of the finely dispersed dye of the constitution and 1.25 parts of ethyl cellulose are dispersed in 44 parts of isopropanol and 44 parts of white spirit (boiling ranges 120° -180° C), containing 7 parts of ethyl cellulose to stabilise the printing ink, until the preparation is completely disaggregated.

The resulting printing ink has very good stability.

Example 7 100 parts of the dyes tuff of the formula are ground in 100 parts of ethanol in the presence of 1 part of Antaron P 804 (water-insoluble polyvinyl pyrolidone, General Aniline and Film Corp. USA) with 200 parts of glass balls until the particle size is in the range of 1 to 3lU The grinding stock is separated from the glass balls and diluted with 100 parts of ethanol. The dispersion is the divided into 3 parts. Into the first 100 parts are stirred 15 parts of ethanol and 5 parts of alcohol-soluble cellulose acetopropionate (Eastman Kodak USA). The dispers- ion has a viscosity of 25 seconds in a Ford measuring cup number 4. Into the second 100 parts are stirred 5 parts of alcohol-soluble cellulose acetobutyrate (Eastman) and the dispersion is diluted with 20 parts of ethanol.

The ink has a viscosity of 30 seconds. The third 100 parts are diluted with 100 parts of ethanol and 2.5 parts of ethyl cellulose N4 (Hercules Cornp. USA) and 2,5 parts of pentalyn 830 (pentaer thritol synthetic resin, Hercules Comp., USA) are stirred in. The ink displays a viscosity of 30 seconds in the Ford measuring cup No, 4.

All three inks are printed on paper and heated together with a polyester fabric for 30 seconds at 210° C, in the course of which very full, red printing designs are formed.

Example 8 100 parts of the dyestuff of the formula are ground in 200 parts of isopropanol in the presence of 1 part of ethyl cellulose with 300 parts of glass bails until the particle size is in the range from 1-3M. The grinding stock is then separated from the glass balls and the resulting dispersion is divided into 3 parts. The first 100 parts are mixed with 10 parts of Pentalyn 830 (pentaerythritol synthetic resin, Hercules Comp. , USA) and parts of isopropanol while stirring thoroughly. The printing ink has a viscosity of 30 seconds in a Ford measuring cup number 4. The second 100 parts are treated with 10 parts of AFS resin (ketone resin from cyclo-hexanone and formaldehyde, Bayer Germany) and 10 parts of isopropanol. The printing ink has a viscosity of 28 seconds,, The third 100 parts are treated with 10 parts of Alresen PA 101 (alkylphenyl resin, Reichhold -Albert Chemie AG, Germany) and 10 parts of isopropanol. The viscosity is 26 seconds. These printing inks produce in intaglio printing very full prints which, when transferred to polyester fabrics as described in Example 7, give very deep prints which can be reproduced three times in succession in approximately the same tinctorial strength with the same paper.

Example 9 300 parts of the dyes tuff of the formula are ground in 700 parts of isopropanol in the presence of 3 parts of ethyl cellulose with 2000 parts of glass balls until the particle size is in the region from 1 to 3 L The dispersion is separated from the glass balls and divided into 3 parts. Into each of these three parts are stirred 10 parts of one of the following synthetic resins: Alresat KM 444 (colophonium maleinate resin), KM 400, KA 945 (colophonium resin modified with acrylic acid), Alftalat AN 420 (non-drying alkyd ' res in) , Alre en PA 101 (alhylphenol resin), Albertol KP 692 (phenol resin modified with colophonium) , all products of Reichhold-Albert Chemie AG, Germany, Pent.alyn 830 (pentaerythritol synthetic resin, Hercules :Comp. , USA) , AFS resin (ketone resin, Bayer), ketone resin N (BASF) and half the amount of Mowital B 30 H (polyvinyl acetal resin, Hoechst) .

All the printing inks have viscosities of under 30 seconds and give full, abrasion-free prints on paper which can be readily transferred.

Example 10 a) 100 parts of the dyestuff of the formula are ground with glass balls in a "DY 0M mill, type KDL, in 200 parts of isopropanol in the presence of Ethocel Ή (Dow) which is added during the grinding in small amounts for for such a time the main amount of dyestuff dcflocculating dyes uff/has been reduced to particles substantially smaller than 5J. 'Altogether 10 parts of Ethocel K 7 are to be added to the paste before completion or the grinding and separation from the grinding elements, b) To this stabilised dispersion is stirred in a solution prepared separately of 24 parts of Alresat KA 945 (a colo-pbonium resin modified with acrylic acid, R ichhold -Albert Chemie) in 155 parts of is'opropanol and neutralised v;ith about 9 parts of a mixture of aliphatic, primary amines . The resulting printing ink manufac ured on pure isopropanol bases with 20% dyestuff content is extraordinarily storage stable, It has a viscosity of below 30 seconds, measured in a Ford measuring cup number 4.

Example 11 To 310 parts of a dispersion manufactured analogous to Example 10 a) of the same dyestuff are stirred in separately prepared solutions consisting of either b) 30 parts of Alftalat AN 420 (non-drying alkyd resin, Reichhols -Albert Chemie) dissolved in 210 parts of ethanol, c) 30 parts of ketone resin A (BASF) dissolved in. 150 parts of ethanol, d) 30 parts of Dertophene P (diphenol terpene resin, Derives Resii-.iques et Terpeniques, France) dissolved in 150 parts of ethanol, or e) 42 parts of Alresat KM 444 (colophonium maleinate resin, Reichhold -Albert Chemie) dissolved in 144 parts of ethanol. The resulting printing inks with 18.2-20, 4% dyes tuff content are based on a solvent mixture of isopropanol and ethanol and can be printed on paper by the intaglic printing process. They have a viscosity of 14-20 seconds measured in a Ford 4 measuring cup.

Example 12 To 310 parts of a dispersion manufactured analogous to Example 10 a) of the same dyes tuff is stirred in a solution prepared separately consisting of 21 parts of Fentalyn 830 (pentaer thritol synthetic resin, Hercules) and an additional 8 parts of Ethocel N 7 (DOW) in 96 parts of pure aliphatic hydrocarbons Isopar E (Esso) and 63 parts of ethanol. The printing ink with 20% dyestuff content is completely de-flocculated and, owing to its low viscosity (26 seconds, Ford 4 cup), highly suitable for intaglio printing on paper.

Example 13 To 310 parts of a dispersion manufactured analogous to Example 10 a) of the same dyestuff are stirred in separately prepared solutions of either b) 27 parts of Alresat KM 444 (colophonium maleinate resin, Reichhold-Albert Chemie) in 96 parts of petroleum distillate which is practically free from aromatic substances and with a boiling range of 110°-140°C, or c) 45 parts of Dertocal 140 (calcium resinate, Derives Resin.iques et Terpeniques, France) in 310 parts of petroleum distillate -with a boiling range of 110°-140°C, in the process of which there result stable intaglio inks of low viscosity (18 seconds, Ford cup 4), which show no signs at all of recrys tallisation after shelf lives lasting iP.onths . 41893/2

Claims (1)

1. CLAIMS Printing inks for the sublimation transfer printing process containing a disperse dyestuff or a dyestuff mixture in fine dispersion which sublimes to and is free from and one or more synthetic resins acting as dyestuff and which printing inks contain a low molecular weight organic solvent in which at room temperature the individual dyestuffs have a maximum solubility of and the synthetic resins a minimum solubility of and have a ure viscosity of 30 measured a Ford measuring cup with a of at least of dyestuff and at least 50 of synthetic Printing inks according to claim which contain a solvent wherein the individual dyestuffs have a mixture solubility at room temperature of Printing inks according to claim which contain as organic solvent alcohols or aliphatic hydrocarbons or mixtures Printing inks according to claim which contain a soluble cellulose acting as dyestuff and or an wherein the contains 2 to 4 carbon atoms and the is an yl group with 2 to 4 a a soluble res from the group of the res ins ketone pol erpen s rubber or of the fied phenol and contain as solvent a mixture of isopropanol or o liquid phatic hydrocarbo or hydrocarbo mixture boiling point is between CO and preferably to Printing according to any one of to which contai a soluble cellulose acting as dyestuf carrier group s 2 to 4 carbon and as solvent a of isopropanol with ethano or or with a liquid aliphatic hydrocarbon or hydrocarbon mixture whose boiling point is between preferably between to Printing inks according to one of claims 1 to contain ethyl cellulose as synthetic Printing inks according to any one of claims 1 to which contain at least of petroleum distillate with range from Printing inks according to any one of claims 1 to which contain at least of Printing inks according to any one of 1 to which contai at least of flat structures which are printed with a ink according to claims 1 to insufficientOCRQuality